Re: [PATCH v4] extcon: Palmas Extcon Driver

[Kishon Vijay Abraham I]

Hi,

On Tuesday 07 May 2013 10:51 AM, Kishon Vijay Abraham I wrote:
> Hi,
>
> On Tuesday 07 May 2013 06:13 AM, myungjoo.ham wrote:
> > > From: Graeme Gregory <gg@xxxxxxxxxxxxxxx>
> > >
> > > This is the driver for the USB comparator built into the palmas chip. It
> > > handles the various USB OTG events that can be generated by cable
> > > insertion/removal.
> > >
> > > Signed-off-by: Graeme Gregory <gg@xxxxxxxxxxxxxxx>
> > > Signed-off-by: Moiz Sonasath <m-sonasath@xxxxxx>
> > > Signed-off-by: Ruchika Kharwar <ruchika@xxxxxx>
> > > Signed-off-by: Kishon Vijay Abraham I <kishon@xxxxxx>
> > > [kishon@xxxxxx: adapted palmas usb driver to use the extcon framework]
> > > Signed-off-by: Sebastien Guiriec <s-guiriec@xxxxxx>
> >
> > Here goes some comments in the code:
> >
> > []
> >
> > > diff --git a/drivers/extcon/extcon-palmas.c
> > b/drivers/extcon/extcon-palmas.c
> > > new file mode 100644
> > > index 0000000..3ef042f
> > > --- /dev/null
> > > +++ b/drivers/extcon/extcon-palmas.c
> > > @@ -0,0 +1,389 @@
> > > +/*
> > > + * Palmas USB transceiver driver
> > > + *
> > > + * Copyright (C) 2013 Texas Instruments Incorporated -
> > > http://www.ti.com
> > > + * This program is free software; you can redistribute it and/or modify
> > > + * it under the terms of the GNU General Public License as published by
> > > + * the Free Software Foundation; either version 2 of the License, or
> > > + * (at your option) any later version.
> > > + *
> > > + * Author: Graeme Gregory <gg@...mlogic.co.uk>
> > > + * Author: Kishon Vijay Abraham I <kishon@...com>
> > > + *
> > > + * Based on twl6030_usb.c
> > > + *
> > > + * Author: Hema HK <hemahk@...com>
> > > + *
> > > + * This program is distributed in the hope that it will be useful,
> > > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > > + * GNU General Public License for more details.
> > > + */
> >
> > Why the email addresses are masked in the source code?
> > (I'm just curious as this is the first time to see such in kernel source)
>
> That was not intentional. Took the previous version from the net. My bad.
> > > +
> > > +#include <linux/module.h>
> > > +#include <linux/init.h>
> > > +#include <linux/interrupt.h>
> > > +#include <linux/platform_device.h>
> > > +#include <linux/io.h>
> > > +#include <linux/usb/phy_companion.h>
> > > +#include <linux/regulator/consumer.h>
> > > +#include <linux/err.h>
> > > +#include <linux/notifier.h>
> > > +#include <linux/slab.h>
> > > +#include <linux/delay.h>
> > > +#include <linux/mfd/palmas.h>
> > > +#include <linux/of.h>
> > > +#include <linux/of_platform.h>
> > > +#include <linux/extcon/extcon_palmas.h>
> > > +
> > > +static const char *palmas_extcon_cable[] = {
> > > +    [0] = "USB",
> > > +    [1] = "USB-HOST",
> >
> >     [1] = "USB-Host",
> >
> > > +    NULL,
> > > +};
> > > +
> > > +static const int mutually_exclusive[] = {0x3, 0x0};
> > > +
> > > +static void palmas_usb_wakeup(struct palmas *palmas, int enable)
> > > +{
> > > +    if (enable)
> > > +        palmas_write(palmas, PALMAS_USB_OTG_BASE, PALMAS_USB_WAKEUP,
> > > +            PALMAS_USB_WAKEUP_ID_WK_UP_COMP);
> > > +    else
> > > +        palmas_write(palmas, PALMAS_USB_OTG_BASE, PALMAS_USB_WAKEUP,
> > 0);
> > > +}
> > > +
> > > +static ssize_t palmas_usb_vbus_show(struct device *dev,
> > > +            struct device_attribute *attr, char *buf)
> > > +{
> > > +    unsigned long        flags;
> > > +    int            ret = -EINVAL;
> > > +    struct palmas_usb    *palmas_usb = dev_get_drvdata(dev);
> > > +
> > > +    spin_lock_irqsave(&palmas_usb->lock, flags);
> >
> > This spinlock is used in this sysfs-show function only.
> > Is this really needed?
> > The only protected value here is "linkstat", which is "readonly"
> > in this protected context.
> > Thus, removing the spin_lock and updating like the following should
> > be the same with less overhead:
> >
> >     int linkstat = palmas_usb->linkstat;
> >     switch(linkstat) {
>
> hmm.. ok.
I think this is to do with disabling interrupts while reporting the VBUS 
state. (linkstat is updated in irq handler). So this should be fine I guess?

Thanks
Kishon
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